Purification of alpha-haloalkylated aromatics



United States Patent 3,282,800 PURIFICATION OF oc-HALOALKYLATED AROMATICS John L. Lang, 42 Windgate Drive, Box 820-111, Murrysville, Pa. N0 Drawing. Filed Aug. 27, 1965, Ser. No. 483,357 7 Claims. (Cl. 203-6) This invention relates to the prevention of thermally induced deterioriation of a-haloal-kyl aromatic compounds.

More particularly, this invention relates to the stabilization of a-haloalkyl aromatic compounds during physical and chemical manipulations in which these compounds are heated for varying time intervals, e.g., distillation.

This application is a continuation-in-part of oopending application Serial No. 210,239, filed July 16, 1962.

Heretofore, the use of such a-haloalkyl aromatic compounds has been limited by the relative instability of these compounds.

There are some instances in the literature and patent art where the problem is dismissed with the blithe statement that such compounds were distilled or some equivalent phrase, but the practical accomplishment of the operation, on a commercial or even the laboratory scale, is at least difficult and in some cases verges on impossibility, for all practical purposes. For instance, some of the potentially most useful compounds of this type can be prepared by a most convenient synthesis, known as chloromethy-lation, a method described by R. C. Fuson and C. H. McKeever in chapter 3 of volume I of Organic Reactions, pp. 63-90 incl., published by John Wiley and Sons, Inc., New York (1942) but the full potential of this synthesis has not been realized because of the difficulties occasioned by thermally induced deterioration during distillation.

The industrial as well as the laboratory scale utility of the a-haloalkyl aromatic compounds, prepared by various methods, have been much less than the constituted functionality thereof would indicate, due for the most part to the difiiculty in purification of the products due to this instability.

None ofthe conventional expedients such as the use of short, relatively ineifectual distillation columns, or Washing with water, slightly alkaline soutions, degassing or the use of anion exchange resins in the stillpot are effective in preventing the thermally deterioration of ozhaloalkylated aromatic compounds.

It is the object of this invention to provide a means for preventing the thermally induced deterioration.

This object and other corollary objects and their ac complishment will become more apparent upon reading the specification and claims of this invention.

It has now been found that a-haloalkylated aromatic compounds can be easily and effectively rendered immune to thermally induced deterioration by the addition of a minor amount of a compound having at least one structural sequence of the type wherein the unoccupied bonds are connected to hydrogen, methylol, or other carbon atoms.

Examples of these acetylenic alcohols which are effective in prevention of thermally induced deterioration of a-h-aloalkylated aromatic compounds are butyne-l,4-d-io.l, and homologs thereof, 3-butyne-2-ol and homologs thereof, 2-phenyl-l-butyne-3-ol, and homologs thereof, 1-ethynyl-cyclohexanol-1 and homologs thereof, l-ethynylcyclohexenol-l and homologs thereof, bis(hydr-oxycyclohexyl) acetylene and homologs thereof; which compounds will be recognized as products of the so-called ethynylation synthesis, pioneered by J. Walter Reppe.

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These compounds can be added over a wide range of effective concentrations; for most purposes, this varies between 0.005% and 5% by weight, based on the a-hal-oalkyl aromatic compound.

Although approximate coincidence of boiling point is not required, and in many cases is deliberately avoided When the product must be free of extraneous materials, to obtain maximum effect in the distillation process, the acetylenic-o1 compound is selected so as to boil in the same general range or higher than the a-haloalkyl aromatic compound whose stabilization is to be effected.

The a-haloalkyl aromatic compounds whose thermally-induced deterioration can be prevented by addition thereto of an acetylenic alcohol are those having the general formula:

R1 t x) i.

wherein A is an aromatic nucleus or substituted aroma-tic nucleus, X is chlorine or bromine, R and R are hydrogen, alkyl groups, derived, substituted or modified alkyl groups, and n is a number from 1 to 3, inclusive.

Examples of such compounds are benzyl chloride, benzyl bromide and their derivatives in which one or more of the hydrogen atoms are replaced by substituents selected from the methyl, ethyl, n-propyl, isopropyl, nbutyl, isobutyl, secondary butyl, tertiary-butyl, v-inyl, isopropeny-l, allyl, (l-chlol'omethyl), (l-ibromoethyl), (1- chloroethyl), (bromomethyl), (l-chloroisopropyl) and (l-brom-oi-sopropyl) substituents. 1-bromoethyl-benzyl chloride may, for example, comprise at least part of the reaction product resulting from the side-chain bromination of ar-chloromethy-lated ethyl benzene; ethyl benzyl chloride may comprise at least a part of the reaction product resulting from the ar-chlor-omethylation of ethyl benzene; vinyl benzyl chloride may comprise at least a part of the dehydrohalogenation product of the side-chain halogenati-on product'of ar-chloromethylated ethyl benzene; and l-chloroethyl benzyl chloride may comprise at least a part of the reaction product resulting from the side-chain chlorination of ar-chloromethyl ethyl benzene.

The temperature range over which the thermally induced deterioration of these a-haloalkyl aromatic compounds can be prevented by the addition of acetylenic alcohols is a broad one. Stabilization has been successful in the range of 55 C. to 200 C., at sub-atmospheric, atmospheric, and super-atmospheric pressures.

The following examples are given to illustrate the invention, and are not to be construed as limiting the invention in any way.

EXAMPLE I A sample of ar-chl-oromethylated ethyl benzene, containing unreacted ethyl benzene, was prepared by the general method described in a chapter by R. C. Fuson and C. H. McKeever in Organic Reactions, volume I, pp. 63-90 incl., John Wiley and Sons, Inc., New York (1942). The product was washed thoroughly with concentrated calcium chloride solution and ice water, dried with calcium chloride and flash distilled by two separate methods:

A. According to the present invention, using an acetylenic alcohol to prevent thermally induced deterioration, and

B. A comparison experiment in which the operations were conducted outside the scope of the invention.

The details of the two portions of the example are:

A. Into a flask containing boiling chips, weighing 343.0 g., was placed 675.5 g. of a mixture containing mainly ethylbenzene and ar-chloromethyl ethylbenzene, plus 2.0

Table I The flask was g. of 3-phenyl-1-butyne-3-ol. The flask was assembled as part of an apparatus consisting of a total-takeoff distillation head, condenser, fraction-cutter, product receiver and a vacuum source, to which was fitted a McLeod type manometer, and included a caustic soda pellet trap and a cold trap whose temperature was maintained by surrounding it with carbon dioxide snow.

- s u a 2m a m H m d W o T s .m o z w 0 a l m s n z d S n t t m 0 e 0 S w .W k 0 h h e e r k b a m B y d f o h d P W n w w. m Vw 5 R o C 4|. a e e a h h r m m mm e w mm m m w E000ooooomnwmmo mnmmnmoonm nmmomu S l 6 C .&0 0 0 0 0 0 Q0 0 0 0 &0 Q0 Q u.. D 0000 00 MDDDDDDDDDDDIDDDDDDDDMmDDDDD mm m m .D m h M m DDDDDDDDDDDDDDDDDDDDMMDD 1D. e O .l C 1 U m 1 O t h an h A m W m w w a M o 012 09240 e, t at .fiawfifiaafiafi .t we a m a t a; stage? n at .3 0000000000000000000000 0011 n W 0 u m a u 5 w 0 QQQQQ0 0 0 0 0 0 0 0 0 0 0 m mQQO O r f d 1 n G 3 f a r m 2 o o n n m I v a m. h n P 0 6 6 DP A 5 S n S C O 1 g m S m w a e C H A n h u e a n c r b y r s e b T b d M m w m n m S 1.0509606703342174655440 03 1 5930844445283 357 we 2 2221221212212222122 4 312 H w n m e m m m w mmw%%%%%%%% m%%mm%%m MmM mm m l .1 O O r. 5 m m m 0 a5 t t a 0 a l a m w m n a t H I W 0 n e o t P e r P a wm n r n e a 0 a 0.0 .0 0 0. e mm m 0 w n t T 5 00200024000 5 05002 678765 33333333333MMMwWwMmm- 1nm nummm M h m n s .m m n w mmwmmmmmwmmmwm%%m%mfimw n T n m e a 0 e o m Tm w. a l w h H c h T A o B d t .n s l 0 1 h l A a L mmm a t e a S g 2 0 1 o e 111122222222%%%%%= 0Wmm nu mu 0 mmwmwflflnmmmmwumn 1 1 Tm m u 1 TN Hun Un i d0 T t a a d0 6 n m I n e H h o W H C m n n n h n n e u n u g t n u u n u m m n M .m n n O J N n n n F n n e T m n t n n n u a m u n u n m c n n n n n n e o n u n n u u n R n n 3 electrically heated, the voltage to the heater was varied by means of a rheostat.

The distillation was conducted under reduced pressure, which was below 10 mm. Hg pressure. in the distillation flask and the temperature in the st head was recorded at short time intervals, and when fractions of the product were removed, the i ternal pressure, 5 the volume distilled, the rheostat setting, the wei ht ofthe fraction, the still head temperature and the flask or i 1 Ofi the scale. I

Product =97,3 (cuts 23-25)/675.5= 14.4%.

As can beseen, the use of an acetylenic alcohol has increased the amount of recovered product from 97.3 g. to 159.0 g.,'or an increase of 63.4% over the technique of the prior art.

EXAMPLE II In another set of-distillations of ethylbenzene-ar-chloromethyl ethylbenzene, in an apparatus similar to that de- Table III Head T, C.

Cale.

Overhead Wt.. g.

Apparent Remarks Sp. Gr.

Mainly Ethylbenzene.

Do. Intermediate. I Chloromethylated product.

Cold Trap=32.7 g. Residue=17.8 g. Product=194.3 (cuts 14-18, incl.). Recovered 194.3/659.5=29.4%.

scribed in Example I except that a 5 section bubble plate B. Usingthe identical apparatus of part A of this excolumn and a fractionating still head was used in place of the flask still total-takeoif head of the previous example. The operation was carried out both in the absence of, and in the presence of acetylenic alcohol, to demonstrate by comparison the resistance to thermally induced deterioration which can be obtained by the use of the teachings of this invention.

A. This part of the experiment Was conducted according to the invention.

ample, but outside the scope of the invention, for purposes of comparison, a distillation was conducted to separate the components of a reaction mixture consisting mainly of ethylbenzene and ar-chloromethylated ethylbenzene. The data obtained are given in Table IV, wherein the internal pressure was corrected to a constant value of 5 mm. Hg pressure as in the previous experiments, and the initial charge was 659.5 g., with no stabilizer added.

Table IV Cut No. Head T, C. Pot T, 0. Overhead Apparent Remarks Cale. Actual Wt., g. Sp. Gr.

14. 8 38 24.2 0.84 Mainly Ethylbenzene. l5. 0 39 24. 8 0.85 Do. 16. 1 43. 5 25. 6 0. 83 D0. 18. 8 46. 4 25. 3 0. 79 D0. 17. 5 47. 3 27. 9 0. 88 Do. 17. 4 49. 0 26. 8 U. 85 D0. 17. 4 49. 0 29. 2 0. 86 Do. 16. 7 50.0 29. 3 0.85 D0. 15. 6 27. 8 0. 84 D0. 16. 4 51 27. 7 0. 84 D0. 15. 8 52 27.8 0.85 D0. 17. 8 57. 0 26. 6 0. 86 Do. 16. 0 62 23. 2 0. 85 D0. 16. 2 27. 0 0.85 Do. 14. 3 101 19. 5 0 84 D0. 13. 2 110. 2 1.0 Column Removed. 83. 6 100 21. 5 1. 00 Chloromethylated product.

87. 0 106 29. 7 1. 03 Do. 90. 6 112 34. 2 1. 04 Do. 99.0 123 33.0 1. 03 D0.

Product=139.6 (cuts 17 through 21).

Into the distillation flask was placed 659.5 g. of ethyl benzene-ar-chloromethylated ethyl benzene reaction mixture, and 0.927 g. of 3-phenyl-l-butyne-3-ol, an acetylenic alcohol. The vacuum distillation was then carried out,

Recovered 128.2/659.5=19.4%.

As can be seen, when the operation is conducted according to the prior art, 128.2 g. of chloromethylated product is obtained, but when an acetylenic alcohol is added in accordance with the present invention, 194.3 g.

of the desired chlorornethylated product is obtained, or an increaseof 51.6%. g

I claim as my invention:

1. A process [for the purification-of an a-haloalkyl aromatic compound having the general formula:

wherein A is a benzene ring in which at least one of the hydrogen atoms is replaced by a substituent selected from the group consisting of the methyl, ethyl,'i'1-propyl, isopropyl, n-butyl, isobutyl, secondary butyl, tertiary butyl, vinyl, isopropenyl, allyl, (l-chloromethyl), (1- bromomethyl), (l-chloroethyl), bromomethyl, (1-ch1oroisopropyl) and (l-bromoisopropyl) substituents, R and R are subst-ituents selected from the group consisting of hydrogen and the lower alkyl groups, X is an atom selected from the group consisti'ngof chlorine and bromine, and n is a number from 1 to 3, inclusive; which 8 ture and distilling the same to produce an "essentially pure a-haloalkyl aromatic compound.

2. The process of claim 1 wherein the qx -hal oalkyl aromatic compound comprises at least a part of the dehydrohalogenation product of the side chain halocomprises the steps of mixing with said compound an i alcohol selected from the group consisting of butyne-l, 4-dio1; homologs of butyne-l, 4-diol; homologs of 3-butyne-2-ol; l-ethynyl-cyclohexanol-l; homologs of l-ethynyl-cyclohexanol-l; l-ethynyl-cyclohexenol-l; homologs of l-ethynyl-cyclohexenol-l; 3- pheny1-1-butyne-3-ol; homologs of 3-phenyl-1-butyne-3- ol; bis-(hydroxycyclohexyl) acetylene; and homologs of bis(hydroxycyclohexyl) acetylene, the amount of said alcohol being at least an amount elfective to prevent thermally induced deterioration of the a-haloalkyl aromatic compound when in the presence of an agent which enhancesdecomposition, and in the presence of an agent which enhances decomposition, adding heat to the mixv genation product of ar-chloromethylated ethyl benzene, and wherein the a-haloalkyl aromatic compound is in the presence of a polymerization catalyst.

5. The process of claim 1 wherein the a-haloalkyl aromatic compound'comprises at least a part of the reaction product resulting from the side-chain chlorination of ar-chloromethyl ethyl benzene.

6. The process of claim 1 wherein the a-haloalkyl aromatic compound comprises vinyl benzyl chloride.

7. The process of claim 1 wherein the a-haloalkyl aromatic compound comprises vinyl benzyl bromide.

References Cited by the Examiner UNITED STATES PATENTS 2,603,622 7/1952 Berger et al. 260-652.5 X 2,775,624 12/1956 Skeeters et al. 260-652.5 2,945,895 7/ 1960 Burch et a1. 260-652.5

LEON ZITVER, Primary Examiner.

K. V. ROCKEY, Assistant Examiner. 

1. A PROCESS FOR THE PURIFICATION OF AN A-HALOALKYL AROMATIC COMPOUND HAVING THE GENERAL FORMULA: 